If you hard drive is noticeably loud, I'd make quick work of backing up your important data and buying a new hard drive (although an SSD would be preferable).

If you're still interested in getting a new video card, check out: http://www.videocardbenchmark.net/high_end_gpus.html, it ranks them by performance and provides recent prices for context.

Also, http://pcpartpicker.com/ will be your new god when buying hardware.